JP2018154004A - Laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated film excellent in adhesibility between a substrate layer and a hard coat layer, and excellent in adhesiveness between layers under high temperature and high humidity.SOLUTION: The laminated film is provided which has a substrate layer (layer A) containing a polyester resin as a main component, and a resin layer (layer B) on at least one surface adjacent to the layer A, and in which a carboxyl terminal group amount of the polyester resin of the layer A is 20 eq/ton or more and 50 eq/ton or less. The laminated film satisfies expression 1: 230≤Tmeta+0.05T, in expression 1, Tmeta represents a minute endothermic peak temperature (°C) of the laminated film obtained by differential scanning calorimetry (DSC), and T represents a thickness (μm) of the laminated film.SELECTED DRAWING: None

Description

  The present invention relates to a laminated film having a base material layer (A layer) containing a polyester resin as a main component and a resin layer (B layer) adjacent to at least one surface of the A layer.

  Thermoplastic resin films, especially biaxially stretched polyester films, have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. Widely used in applications.

  In recent years, polyester films have been used in various optical films, particularly in display member applications such as touch panels, liquid crystal display panels (LCD), plasma display panels (PDP), and organic electroluminescence (organic EL).

  In particular, in such applications, a hard coat film in which a hard coat layer is laminated on a polyester film is used. Moreover, in order to improve the adhesiveness of the polyester film which is a base material, and a hard-coat layer, as these intermediate layers, the resin layer which has easy adhesiveness (henceforth, the resin layer which has easy adhesiveness is referred to as an easily adhesive layer) Are often provided).

  The hard coat film is required to have adhesion with a substrate at room temperature, further under high temperature and high humidity, transparency, scratch resistance, antifouling property and the like. Moreover, since it is often used on the surface of a display or the like, the hard coat film is required to have visibility and design. When a hard coat layer is laminated on a polyester film that is a base material, if the refractive index of the hard coat layer and the polyester film that is the base material is different, interference spots due to interface reflection occur and visibility deteriorates. There is a need for reduction of interference spots. Therefore, even when the refractive index adjustment layer (AR layer, index matching layer) or antifouling layer is formed on the hard coat layer, the visibility of the image display device or the like deteriorates or the sense of quality is impaired. There is.

  On the other hand, when a refractive index adjustment layer composed of a high refractive index layer / low refractive index layer is laminated on the surface of the hard coat layer, by increasing the refractive index of the hard coat layer, high refractive index from the refractive index adjustment layer. The rate layer can be omitted. As a result, in the film production process, the cost can be greatly reduced without impairing the function. This technology has attracted attention due to the recent strong demand for cost reduction.

When a hard coat layer having a high refractive index (for example, a refractive index of 1.63) is provided on a base polyester film (for example, a refractive index of 1.66), as a method of suppressing interference spots,
A method (Patent Documents 1 and 2) is disclosed in which an easy-adhesion layer having a high refractive index having an intermediate refractive index (1.63 to 1.66) is provided between the hard coat layer and the base film. . Furthermore, interference spots when a high refractive index hard coat layer having an easy-adhesion layer made of a water-soluble polyester resin, a metal oxide particle having a number average particle size of 3 nm to 50 nm or less, and a cross-linking agent such as an oxazoline-based compound is laminated. And a laminated film excellent in adhesion to the high refractive index hard coat layer has been proposed (Patent Document 3).

Japanese Patent No. 3632044 JP 2004-54161 A International Publication No. 2013/137101 Pamphlet

  In recent years, with the further increase in screen size, higher definition, and diversification of usage environments in the display field, the level of demand for compatibility between interlaminar adhesion and high transparency especially after moisture-resistant heat treatment is increasing.

In the methods of Patent Documents 1 and 2, respectively, a method of adding a water-soluble metal chelate compound or metal acylate compound to a water-soluble polyester resin (Patent Document 1), a polymer binder and metal oxide particles having a high refractive index are added. A method (Patent Document 2) has been proposed. However, a large amount of nano-order fine particles must be added. When nano-order fine particles are used, the surface area of the fine particles increases dramatically, causing a problem of aggregation and a decrease in transparency. Further, when the fine particles are aggregated, the refractive index in the surface of the resin layer becomes non-uniform, and there is a problem that the suppression of interference spots is also reduced. Furthermore, in the resin layer, in the portion where the fine particles are aggregated, the ratio of the binder component that contributes to the adhesiveness to the hard coat layer is relatively reduced, so that there is a problem that the adhesiveness is also reduced.
In Patent Document 3, by selecting the particle size of the metal oxide particles and the component of the easy-adhesion layer, interference spots when the high-refractive index layer is laminated are suppressed, and the adhesiveness with the high-refractive index layer is improved. It is disclosed. However, in the method described in Patent Document 3, peeling may occur in a high temperature and high humidity environment. Therefore, an object of the present invention is to provide a laminated film excellent in adhesiveness with a hard coat layer and adhesiveness under high temperature and high humidity.

In order to solve the above problems, the laminated film of the present invention has the following configuration.
(1) A laminated film having a base material layer (A layer) mainly composed of a polyester resin and a resin layer (B layer) adjacent to at least one surface of the A layer, the polyester resin of the A layer The amount of carboxyl end groups is 20 eq / ton or more and 60 eq / ton or less, and satisfies the following formula 1.

230 ≦ Tmeta + 0.05T (Formula A)
(However, the above-mentioned Tmeta is a minute endothermic peak temperature (° C.) obtained by differential scanning calorimetry (DSC) of the laminated film, and T is the laminated film thickness (μm).)
(2) The laminated film according to (1), wherein the laminated film satisfies the following formula 2.
Tmeta + 0.05T ≦ 245 (Formula B)
(3) The laminated film according to any one of (1) and (2), wherein the resin layer (B layer) has a thickness Tb of 5 to 120 nm.
(4) The laminated film according to any one of (1) to (3), wherein the resin layer (B layer) is a layer containing a polyester resin as a main component.
(5) The resin layer (B layer) is a polyester resin (a), metal oxide particles (b), an acrylic resin (c), a component (d1) derived from an oxazoline-based compound, and / or a melamine type The laminated film according to any one of (1) to (4), which contains a component (d2) derived from a compound.
(6) A coating composition in which the resin layer (B layer) contains a polyester resin (a), metal oxide particles (b), an acrylic resin (c), an oxazoline-based compound and / or a melamine-based compound. The laminated film according to any one of (1) to (5), which is obtained by heating.
(7) The laminated film according to any one of (1) to (6), which is used for display applications.

  ADVANTAGE OF THE INVENTION According to this invention, the laminated | multilayer film excellent in adhesiveness with a hard-coat layer and the adhesiveness under high temperature and high humidity can be provided.

The laminated film of the present invention has a base material layer (A layer) containing a polyester resin as a main component and a resin layer (B layer) on at least one surface adjacent to the A layer.
In the present invention, the polyester constituting the polyester resin as the main component of the base material layer (A layer) is a general term for polymers having an ester bond as the main bond chain of the main chain. Preferred polyesters include those having at least one constituent resin selected from ethylene terephthalate, ethylene-2,6-naphthalate, butylene terephthalate, propylene terephthalate, 1,4-cyclohexanedimethylene terephthalate, and the like as a main constituent resin. Can be mentioned. These constituent resins may be used alone or in combination of two or more. The intrinsic viscosity (measured in o-chlorophenol at 25 ° C.) of the above-mentioned polyester is preferably 0.4 to 1.2 dl / g, more preferably 0.5 to 0.8 dl / g. Is suitable for carrying out the present invention.

  In the polyester, various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic lubricant, a pigment, a dye, organic or inorganic fine particles, a filler, an antistatic agent. Further, a nucleating agent and a crosslinking agent may be added to such an extent that the characteristics are not deteriorated.

  Moreover, it is preferable to use a biaxially oriented polyester film as a base material layer (A layer) of the laminated film of the present invention. Here, “biaxial orientation” refers to a pattern showing a biaxial orientation pattern by wide-angle X-ray diffraction. In general, the biaxially oriented polyester film can be obtained by stretching an unstretched polyester sheet by about 2.5 to 5 times in the sheet longitudinal direction and in the width direction, and then performing heat treatment.

  The base material layer (A layer) may be a laminated structure of two or more layers. As the laminated structure, for example, a composite film having an inner layer portion and a surface layer portion, in which a particle is substantially not contained in the inner layer portion and a layer containing particles only in the surface layer portion is provided. A film can be mentioned. Further, the polyester constituting the inner layer portion and the surface layer portion may be the same or different.

  In the laminated film of the present invention, the thickness (T) of the laminated film is not particularly limited and is appropriately selected depending on the application and type, but is selected within a range satisfying (Formula A) described later. In view of mechanical strength, handling properties, etc., the thickness is preferably 10 to 500 μm, more preferably 23 to 250 μm. The polyester film may be a composite film obtained by coextrusion.

The laminated film in the present invention needs to satisfy the following (formula A).
230 ≦ Tmeta + 0.05T (Formula A)
(However, the above-mentioned Tmeta is a minute endothermic peak temperature (Tmeta) (° C.) obtained by differential scanning calorimetry (DSC) of the laminated film, and T is the thickness (T) (μm) of the laminated film.)
When Tmeta + 0.05T is less than 230, the wet heat resistant adhesion between the base material layer (A layer) and the resin layer (B layer) is deteriorated. Moreover, it is preferable that the value of Tmeta + 0.05T is 245 or less from a viewpoint of the planarity of a laminated film. Tmeta is a value corresponding to the amount of heat applied to the film in the heat treatment step, and the higher the value, the higher the temperature and the longer the heat treatment. In the process for producing a biaxially oriented film, the heat treatment step applies heat to the biaxially oriented film, thereby increasing the crystallinity of the polyester molecules in the film and imparting thermal stability and the like. In this step, the molecular regularity of a part of the amorphous component is relaxed simultaneously with the crystal growth in the molecule. The presence of the amorphous part with relaxed orientation is considered to increase the affinity with the adhesive layer and improve the adhesiveness and adhesion durability. When Tmeta is less than 220 ° C., adhesion and adhesion durability may decrease. Tmeta is preferably 225 ° C. or more and 235 ° C. or less, and if it exceeds 235 ° C., stable production may not be possible due to film breakage during heat treatment, and moisture and heat resistance performance may be reduced. The method for bringing Tmeta and T into the range of the above (formula A) is not particularly limited.

  The amount of carboxyl end groups of the base material layer (A layer) mainly composed of the polyester resin of the laminated film of the present invention needs to be 20 to 60 eq / ton. More preferably, it is 25-50 eq / ton, More preferably, it is 30-45 eq / ton. In the prior art, the amount of carboxyl end groups in a layer mainly composed of a polyester resin has been considered to be preferably small from the viewpoints of heat resistance and moist heat resistance. However, as a result of intensive studies by the present inventors, in the laminated film satisfying Tmeta + 0.05T of 230 or more, when the amount of carboxyl end groups of the base material layer (A layer) is decreased, the amount rapidly decreases below a certain amount. It was found that the initial adhesion between the base material layer (A layer) and the resin layer (B layer) and the wet heat resistance are reduced. At present, it is not clear by what mechanism this effect can be obtained, but if a large heat load is applied in the heat treatment step so that the above Tmeta + 0.05T satisfies 230 or more, the base material layer (A layer) It is presumed that the carboxyl end groups present in the vicinity of the surface of (A) and the reaction end groups of the resin layer (B layer) react to contribute to improving the adhesion between the A layer and the B layer. In the examples described below, the present inventors conducted adhesion evaluation on laminated films having various carboxyl end group amounts, Tmeta, and T. As a result, laminated end films in which the carboxyl end group amounts, Tmeta, and T do not satisfy the above conditions. Is peeled off between the A layer and the B layer (peeling occurs at the interface between the A layer and the B layer), whereas the laminated film satisfying the above conditions for the carboxyl end group amount, Tmeta, T is A Since peeling between the layer and the B layer is suppressed, the mechanism as described above is estimated. From the viewpoint of improving the adhesion between the base material layer (A layer) and the resin layer (B layer), the base material layer (A layer) preferably has a larger amount of carboxyl end groups, but the carboxyl end group content is 60 eq / ton. When it is above, the laminated film is colored to impair transparency. In addition, when the carboxyl end group amount is 60 eq / ton or more, although the initial adhesion is good, the wet heat resistance is lowered.

  Since the amount of carboxyl terminal groups of the polyester raw material increases in the melted state at the time of melt film formation, the value should be 2 to 10 eq / ton lower than the target value of the terminal carboxyl groups in the polyester resin constituting the laminated film. Is preferred. In order to reduce the degradation of the polyester resin during melting, the moisture content in the polyester resin is reduced to 50 ppm or less in advance by a method such as heating the polyester resin under reduced pressure, or the film is melted into the film. The temperature of the polyester resin at the time of extrusion film formation is set to the melting point (Tm) of the polyester resin + 40 ° C. or less, and the time from landing of the extruder to the casting drum is shortened. Is preferably 5 minutes or less, particularly preferably 3 minutes or less.

  The thickness of the resin layer (B layer) in the laminated film of the present invention is preferably in the range of 5 to 120 nm. More preferably, it is 20-100 nm. By setting it as the said range, since it becomes possible to fully express the interference spot after apply | coating a hard coat to the laminated | multilayer film of this invention, it is preferable.

  The resin layer (B layer) in the laminated film of the present invention preferably contains a polyester resin as a main component. Furthermore, from the viewpoint of adhesiveness and suppression of interference spots after hard coat coating, the polyester resin (a), the metal oxide particles (b), the acrylic resin (c), and the component derived from the oxazoline-based compound (d1) And / or a component (d2) derived from a melamine compound is preferred. Furthermore, the polyester resin (a) preferably has a fluorene skeleton and / or a naphthalene skeleton. By adding a fluorene skeleton and / or naphthalene skeleton to the polyester resin (a), it is possible to increase the refractive index of the polyester resin, reduce interference spots after hard coat coating, and increase the glass transition temperature of the polyester resin. Therefore, the heat resistance characteristic of the adhesive force is improved, which is preferable.

  The polyester resin (a) having a fluorene structure used in the present invention refers to a polyester resin having an ester bond in the main chain or side chain, and can be obtained by the following method I) or II). In addition, there is also a method using I) and II) in combination (a method in which a dicarboxylic acid component (aa), a glycol component (ab), and a component (ac) are used as constituent components and these are subjected to a polycondensation reaction). It may be used.

I) A method in which a dicarboxylic acid component (a-a) and a glycol component (a-b) are used as constituent components and both are subjected to a polycondensation reaction,
II) A method in which a component (ac) having at least one alcoholic group (hydroxyl group) and at least one carboxyl group is used as a constituent component and a polycondensation reaction is performed.

In the method I), the dicarboxylic acid component (aa) is classified into a dicarboxylic acid component (aa ₁ ) having a fluorene structure and a dicarboxylic acid component (aa ₂ ) having no fluorene structure. . The glycol component (ab) is classified into a glycol component (ab- ₁ ) having a fluorene structure and a glycol component (ab- ₂ ) having no fluorene structure. In the present invention, in order to introduce a fluorene structure into the polyester resin, a dicarboxylic acid component (a-a ₁ ) having a fluorene structure and / or a glycol component (a-b ₁ ) having a fluorene structure are copolymerized. Is preferred.

In the method II), the component (ac) is classified into a component (Dc ₁ ) having a fluorene structure and a component (ac ₂ ) having no fluorene structure. In this invention, in order to introduce | transduce a fluorene structure into a polyester resin (a), it is preferable that the component (ac- ₁ ) which has a fluorene structure is copolymerized.

  Hereinafter, the polyester resin (a) having a fluorene structure (hereinafter sometimes referred to as “fluorene copolymerized polyester resin (a)”) will be described in detail in the case of using the method of I). The method is the same as the method of I).

  First, in the present invention, the dicarboxylic acid component (aa) includes an ester-forming derivative obtained by alkylating a dicarboxylic acid. The dicarboxylic acid component (aa) includes not only a narrowly defined dicarboxylic acid but also a trivalent or higher polyvalent carboxylic acid. The dicarboxylic acid component (aa) includes an acid anhydride.

  In the present invention, the glycol component (aa) includes not only a narrowly-defined glycol but also a trivalent or higher polyol.

Examples of the dicarboxylic acid component (a-a ₁ ) having a fluorene structure include 9,9-bis (t-butoxycarbonylmethyl) fluorene, 9,9-bis [2- (t-butoxycarbonyl) ethyl] fluorene, 9,9-bis [1- (t-butoxycarbonyl) ethyl] fluorene, 9,9-bis [2- (t-butoxycarbonyl) -1-methylpropyl] fluorene, 9,9-bis [2- (t -Butoxycarbonyl) butyl] fluorene, 9,9-bis [5- (t-butoxycarbonyl) pentyl] fluorene, and the like, but are not limited thereto.

Examples of the dicarboxylic acid component not having a fluorene structure (a-a _2), an aromatic having no fluorene structure, aliphatic, dicarboxylic acids and trivalent or higher-valent carboxylic acid alicyclic be used. In the present invention, as the dicarboxylic acid component (aa- ₂ ), terephthalic acid, isophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1 , 2-bisphenoxyethane-p, p′-dicarboxylic acid, and the like can be used. Examples of the aliphatic and alicyclic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-cyclohexanedicarboxylic acid and the like, and ester-forming derivatives thereof can be used.

As the glycol component (ab- ₁ ) having a fluorene structure, 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-methyl Phenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-diisopropylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-dibenzylphenyl Fluorene, 9,9-bis [4- (3-hydroxypropoxy) phenyl] fluorene 9,9-bis [4- (4-hydroxybutoxy) phenyl] fluorene, and the like, but are not limited thereto. Absent.

Examples of the glycol component having no fluorene structure (ab- ₂ ) include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,7-heptanediol, 1,10-decanediol, neopentyl glycol, 4,4′-dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4′- Although isopropylidenephenol, cyclopentane-1,2-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol and the like can be used, it is not limited thereto.

The amount of the dicarboxylic acid component (a-a ₁ ) having a fluorene structure in the fluorene copolymerized polyester resin (a) is equal to the amount of the dicarboxylic acid component (aa) constituting the fluorene copolymerized polyester resin (a). It is preferable that it is 40 mol% or more with respect to it, More preferably, it is 80 mol% or more. Although an upper limit is not specifically limited, It is preferable that it is 95 mol% or less.

The copolymerization amount of the glycol component (a-b ₁ ) having a fluorene structure in the fluorene copolymer polyester resin (a) is based on the amount of the glycol component (Db) constituting the fluorene copolymer polyester resin (a). It is preferably 40 mol% or more, more preferably 80 mol% or more. The upper limit is not particularly limited, but is particularly preferably 95 mol% or less.

When the copolymerization amount of the dicarboxylic acid component (a-a ₁ ) or glycol component (a-b ₁ ) having a fluorene structure is less than 40 mol%, the fluorene copolymerized polyester resin (a) is not sufficiently high in refractive index. There is a possibility. The upper limit is not particularly limited, but if the copolymerization ratio exceeds 95 mol%, the glass transition temperature of the fluorene copolymerized polyester resin (a) becomes high, and the resin layer is formed using an in-line coating method described later. When the film is provided, the stretchable followability becomes poor, and a uniform resin layer may not be provided.

In addition, the copolymerization amount of the dicarboxylic acid component a-Da ₁ ) having a fluorene structure and the glycol component (a-b ₁ ) having a fluorene structure in the fluorene copolymer polyester resin (a) is determined by the fluorene copolymer polyester resin (a). When the total amount of the dicarboxylic acid component (aa) and the glycol component (ab) constituting the component is 100 mol%, it is preferably 20 mol% or more, more preferably 40 mol% or more. is there. Although an upper limit is not specifically limited, It is preferable that it is 50 mol% or less.

In the present invention, the fluorene copolymer polyester resin (a) is preferably water-soluble. In order to make the fluorene copolymerized polyester resin (a) water-soluble, it is necessary to introduce a hydrophilic component such as a compound containing a carboxylate group or a compound containing a sulfonate group into the side chain of the polyester resin (a). preferable. The introduction of the hydrophilic component uses a dicarboxylic acid component (a-a ₃ ) having a sulfonate group or a trivalent or higher polyvalent carboxylic acid component (b-a ₄ ) as the dicarboxylic acid component (b-a). Can be achieved.

Examples of the dicarboxylic acid component (Da ₃ ) having a sulfonate group include sulfoisophthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7dicarboxylic 5 [4-sulfophenoxy] isophthalic acid. Examples include alkali metal salts and alkaline earth metal salts.

As the trivalent or higher polyvalent carboxylic acid component (Da ₄ ), an acid anhydride can be used in addition to a polyvalent carboxylic acid such as trimellitic acid. Specifically, trimellitic anhydride, 1,2,4,5-butanetetracarboxylic dianhydride (pyromellitic anhydride), 1,2,3,4-pentanetetracarboxylic dianhydride, 3, 3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, cyclopentanetetra Carboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, ethylene glycol bistrimellitic dianhydride, 2,2 Examples include ', 3,3'-diphenyltetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, and ethylenetetracarboxylic dianhydride.

  However, in applications requiring resistance to moisture and heat resistance, as represented by recent display applications, when a sulfonate group is used as the hydrophilic component of the polyester resin (a), the hydrophilicity of the sulfonate group is strong. The adhesiveness with the hard coat layer under high-temperature and high-humidity conditions with the adherend may be reduced.

Therefore, in the present invention, the fluorene copolymer polyester resin (a) does not have a dicarboxylic acid component (a-a ₃ ) having a sulfonate group, or the dicarboxylic acid component (a) constituting the fluorene copolymer polyester resin (a) ( It is preferred to have less than 0.1 mol% relative to the amount of aa). The amount of the dicarboxylic acid component (a-a ₃ ) having a sulfonate group is more preferably 0.05 mol% or less, and particularly preferably not (0 mol%).

Therefore, in the present invention, when imparting hydrophilicity (water solubility) to the fluorene copolymerized polyester resin (a), it is preferable to copolymerize a trivalent or higher polyvalent carboxylic acid component (a-a ₄ ). By copolymerizing a trivalent or higher polyvalent carboxylic acid component (a-a ₄ ), a carboxyl group can be introduced into the side chain of the polyester resin (a). Moreover, it is good also as a carboxylate group by neutralizing this carboxyl group with ammonia, sodium hydroxide, etc. By using a carboxylate group, the hydrophilicity can be further enhanced.

In the present invention, it is more preferable to use tetracarboxylic acid as the trivalent or higher polyvalent carboxylic acid component (a-a ₄ ). Tetracarboxylic acid has more carboxyl groups than trivalent carboxylic acid such as trimellitic acid, and is necessary for imparting hydrophilicity to fluorene copolymer polyester resin (a). Fluorene copolymer polyester resin The proportion of the polyvalent carboxylic acid component (aa ₄ ) in the dicarboxylic acid component (aa) in (a) can be reduced. Thereby, the number average molecular weight at the time of polymerizing the polyester resin can be sufficiently increased, and the adhesion with the high refractive index hard coat layer to be laminated can be improved.

In the copolymerization of the polyvalent carboxylic acid component, a trivalent or higher polyvalent carboxylic acid anhydride is added to the polyester polyol (polyester oligomer) obtained by reacting the dicarboxylic acid component (aa) and the glycol component (ab). It is preferable to use a method in which a carboxyl group is introduced into the side chain of the polyester resin (a) by reacting the product (a-a ₄ ). By using this method, a carboxyl group can be more efficiently introduced into the side chain of the polyester resin (a).

The amount of polycarboxylic acid anhydride (a-a ₄ ) used at this time (a-a ₄ m (mol)) is the amount of glycol component (Da) used in the esterification reaction (Dam (mol)). ) And the substance amount (a-bm (mol)) of the dicarboxylic acid component (a-am-a-bm (mol)) is preferably 0.5 to 1.0 times the substance amount. If it is set as the said preferable range, it will be excellent in the adhesiveness under the high-temperature, high-humidity conditions to the base material of this prepared resin layer, On the other hand, the number average molecular weight of polyester will fully raise.

Next, an example of a method for producing the fluorene copolymer polyester resin (a) will be described. First, succinic acid or an ester-forming derivative thereof is used as the dicarboxylic acid component (a-a ₂ ) having no fluorene structure, and 9,9-bis [4- (2) is used as the glycol component (a-a ₁ ) having a fluorene structure. -Hydroxyethoxy) phenyl] fluorene is subjected to an esterification reaction using a glycol component such as ethylene glycol and a catalyst as a glycol component (ab- ₂ ) having no fluorene structure to obtain a polyester polyol. At this time, it is preferable that the addition amount of 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene and ethylene glycol is 1.01 to 2.0 times mol with respect to all the dicarboxylic acid components. Within the above preferred range, the polyester polyol can be polymerized smoothly in the presence of an excess glycol component, while the number average molecular weight distribution of the polyester resin is sufficiently increased.

  Catalysts include titanium-based catalysts such as tetraisopropyl titanate and tetra-n-butyl titanate, antimony-based compounds such as antimony trioxide, germanium-based catalysts such as germanium oxide, and catalysts such as zinc acetate, manganese acetate, and dibutyltin oxide. Preferably, tetra-n-butyl titanate is used. The esterification reaction at this time is not particularly limited by temperature and time, and may be carried out within a known range.

Next, polycarboxylic acid anhydride (Da ₄ ) is added to the obtained polyester polyol. If this reaction is carried out at 160 to 200 ° C. for about 1 to 10 hours, the desired polyester polyol is obtained. At this time, the catalyst may be added to the same extent.

  In the present invention, the intrinsic viscosity of the fluorene copolymerized polyester resin (a) is not particularly limited, but is 0.3 dl / g or more in order to improve the adhesion to an adherend such as a hard coat layer. Is preferred. The upper limit of the intrinsic viscosity is not particularly limited, but is preferably 0.8 dl / g or less from the viewpoint of handling properties. The fluorene copolymerized polyester resin (a) having a desired intrinsic viscosity can be obtained by adjusting melt polymerization conditions such as polymerization time and polymerization temperature.

Further, the glass transition point of the fluorene copolymerized polyester resin (a) (hereinafter sometimes abbreviated as Tg) is preferably 50 to 170 ° C, more preferably 50 to 150 ° C. When it is in the above preferred range, the wet heat adhesiveness is excellent, and on the other hand, the resin layer can be uniformly coated by an in-line coating method described later. In order to make Tg within the above range, a method of using an aliphatic dicarboxylic acid component as the dicarboxylic acid component (aa- ₂ ) other than the dicarboxylic acid component having a fluorene structure of the fluorene copolymerized polyester resin (a) is used. is there.

Further, the acid value of the fluorene copolymerized polyester resin (a) is preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more. By setting the acid value within the above range, the adhesion with the hard coat layer, particularly the wet heat adhesion can be improved. The acid value to the above range is obtained by the polymerization time of the fluorene copolymerized polyester resin (a), to adjust the amount of polycarboxylic acid anhydride to be reacted with the polyester polyol (a-a ₄₎ .

  In the laminated film of the present invention, the resin layer (B layer) preferably contains metal oxide particles (b). By using the metal oxide particles (b), the refractive index of the resin layer (B layer) can be increased. As a result, interference spots at the time of laminating the hard coat layer can be suppressed. In addition, the metal oxide particles (b) in the present invention are excellent in malleability and ductility, are good electrical and thermal conductors, and have a metallic luster, that is, in the periodic table, boron (B), silicon (Si), It refers to oxide fine particles of elements located to the left of the diagonal line connecting arsenic (As), tellurium (Te) and astatine (At). Further, oxide fine particles of an element located on the right side of the alkaline earth metal (Group 2) in the periodic table are preferable.

As such metal oxide fine particles, from the viewpoint of suppression of interference spots, metal oxide particles having a high refractive index, preferably metal oxide particles having a refractive index of 1.6 or more are suitable. Examples of the high refractive index metal oxide particles include TiO ₂ , ZrO ₂ , ZnO, CeO ₂ , SnO ₂ , Sb ₂ O ₅ , indium-doped tin oxide (ITO), phosphorus-doped tin oxide (PTO), Y ₂ O ₅ , _{la 2 O 3, Al 2 O} 3, and the like.

These metal oxide particles may be used individually by 1 type, and may be used in combination of 2 or more type. From the viewpoints of dispersion stability and refractive index, titanium oxide particles (TiO ₂ ) and / or zirconium oxide particles (ZrO ₂ ) are particularly preferable.

  In the present invention, the resin layer (B layer) is preferably formed from a coating composition containing an acrylic resin (c). When the acrylic resin (c) is contained in the coating composition, it is possible to obtain a film that suppresses aggregation of the metal oxide particles (b), has excellent transparency, and suppresses interference spots.

  The acrylic resin (c) comprises a monomer unit (c1) represented by the formula (1), a monomer unit (c2) represented by the formula (2), and a monomer unit (c3) represented by the formula (3). It is preferable that it is resin which has.

(In Formula (1), the R1 group represents a hydrogen atom or a methyl group. N represents an integer of 9 or more and 34 or less).

(In Formula (2), the R2 group represents a hydrogen atom or a methyl group. The R4 group represents a group containing two or more saturated carbocycles).

(In Formula (3), the R3 group represents a hydrogen atom or a methyl group. The R5 group represents a hydroxyl group, a carboxyl group, a tertiary amino group, a quaternary ammonium base, a sulfonic acid group, or a phosphoric acid group. Represents.)
Here, the acrylic resin (c) in the present invention is preferably a resin having a monomer unit (c1) represented by the formula (1).

  In the formula (1), it is preferable to use an acrylic resin having a monomer unit in which n is 9 or more and 34 or less because the dispersibility of the metal oxide particles (b) in the aqueous solvent becomes stable. It is preferable to use an acrylic resin having a monomer unit in which n in the formula (1) is 9 or more and 34 or less because the aggregation or precipitation of the metal oxide particles (b) in the resin composition can be suppressed. Moreover, since aggregation of a metal oxide particle (b) can be suppressed in a drying process, it is preferable. As a result, the laminated film having good transparency, and further, interference spots at the time of laminating the high refractive index hard coat layer are good, which is preferable.

  In order that the acrylic resin in the present invention has the monomer unit (c1) represented by the formula (1), the (meth) acrylate monomer (c1 ′) represented by the following formula (4) is used as a raw material, It is more preferable to polymerize.

  The (meth) acrylate monomer (c1 ′) is preferably a (meth) acrylate monomer represented by an integer of 9 to 34 in the formula (4), more preferably 11 to 32 (meth) acrylate. Monomers, more preferably 13 to 30 (meth) acrylate monomers.

  The (meth) acrylate monomer (c1 ′) is not particularly limited as long as it is a (meth) acrylate monomer in which n in the formula (4) is 9 or more and 34 or less, but specifically, decyl (meth) acrylate, dodecyl (meta ) Acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, 1-methyltridecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, eicosyl (meth) acrylate, docosyl (meth) acrylate, tetracosyl (Meth) acrylate, triacontyl (meth) acrylate, etc. are mentioned, and dodecyl (meth) acrylate and tridecyl (meth) acrylate are particularly preferable. These may be used alone or in a mixture of two or more.

  Moreover, it is important that the acrylic resin in the present invention is a resin having the monomer unit (b2) represented by the formula (2).

  In the formula (2), when an acrylic resin having a monomer unit containing two or more saturated carbocycles is used, the function as steric hindrance acts effectively, and the metal oxide particles (b) can suppress aggregation or sedimentation. Further, it is preferable because aggregation of the metal oxide particles (b) can be suppressed in the drying step.

  As a result, the interference film at the time of lamination | stacking with a favorable transparent film and a high refractive index hard coat layer becomes favorable, and since adhesiveness with a hard-coat layer becomes favorable, it is preferable.

  In order that the acrylic resin (c) in the present invention has the monomer unit (c2) represented by the formula (2), the (meth) acrylate monomer (c2 ′) represented by the following formula (5) is used as a raw material. It is preferable to use and polymerize.

  As the (meth) acrylate monomer (c2 ′) represented by the formula (5), a bridged condensed cyclic formula (having a structure in which two or more rings each share two atoms and bonded), Various cyclic structures such as spirocyclic (having a structure in which two cyclic structures are shared by sharing one carbon atom), specifically, compounds having a bicyclo, tricyclo, tetracyclo group, etc. can be exemplified. Of these, (meth) acrylates containing a bicyclo group are particularly preferred from the viewpoint of compatibility with the binder.

  Examples of the (meth) acrylate containing the bicyclo group include isobornyl (meth) acrylate, bornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, adamantyl (meth) acrylate, and dimethyladamantyl (Meth) acrylate etc. are mentioned, and isobornyl (meth) acrylate is particularly preferred.

  Furthermore, the acrylic resin in the present invention is preferably a resin having a monomer unit (c3) represented by the formula (3).

  When an acrylic resin in which the R5 group in the formula (3) has a monomer unit of a hydroxyl group, a carboxyl group, a tertiary amino group, a quaternary ammonium group, a sulfonic acid group, or a phosphoric acid group is used, the acrylic resin enters the aqueous solvent. In the resin composition, acrylic resin and metal oxide particles (b) can be uniformly dispersed in an aqueous solvent, and the aggregation of metal oxide particles (b) is suppressed in the drying process. This is preferable because it is possible.

  In order that the acrylic resin in this invention has the monomer unit (c3) represented by Formula (3), it polymerizes using the (meth) acrylate monomer (c3 ') represented by Formula (6) as a raw material. It is necessary.

  Examples of the (meth) acrylate monomer (c3 ′) represented by the formula (6) include the following compounds.

  As the (meth) acrylate monomer having a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2,3-dihydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polyethylene Examples include monoesterified products of polyhydric alcohols such as glycol mono (meth) acrylate and (meth) acrylic acid, or compounds obtained by ring-opening polymerization of ε-caprolapton on the monoesterified product, and particularly 2-hydroxyethyl ( (Meth) acrylate and 2-hydroxypropyl (meth) acrylate are preferred.

  Examples of the (meth) acrylate monomer having a carboxyl group include α, β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid, or hydroxyalkyl (meth) acrylate and acid anhydrides. A half esterified product of Acrylic acid and methacrylic acid are particularly preferable.

  Tertiary amino group-containing monomers include N, N-, such as N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, and the like. N, N-dialkylamino such as dialkylaminoalkyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide Examples thereof include alkyl (meth) acrylamide, and N, N-dimethylaminoethyl (meth) acrylate is particularly preferable.

  As the quaternary ammonium base-containing monomer, a monomer obtained by allowing a quaternizing agent such as epihalohydrin, benzyl halide, or alkyl halide to act on the above-mentioned tertiary amino group-containing monomer is preferable. Specifically, 2- (methacryloyloxy ) (Meth) acryloyloxyalkyltrialkylammonium salts such as ethyl trimethylammonium chloride, 2- (methacryloyloxy) ethyltrimethylammonium bromide, 2- (methacryloyloxy) ethyltrimethylammonium dimethyl phosphate, methacryloylaminopropyltrimethylammonium chloride, methacryloyl (Meth) acryloylaminoalkyltrialkylammonium salts such as aminopropyltrimethylammonium bromide, tetrabutylan Tetra (meth) acrylates such as bromide (meth) acrylate, and tri-alkyl benzyl ammonium (meth) acrylates such as trimethylbenzylammonium (meth) acrylate. In particular 2- (methacryloyloxy) ethyl trimethyl ammonium chloride are preferred.

  Examples of the sulfonic acid group-containing monomer include (meth) acrylamide-alkanesulfonic acid such as butylacrylamidesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid, or sulfoalkyl (meth) such as 2-sulfoethyl (meth) acrylate. An acrylate etc. are mentioned, 2-sulfoethyl (meth) acrylate is especially preferable.

  Examples of the phosphoric acid group-containing acrylic monomer include acid phosphooxyethyl (meth) acrylate, and acid phosphooxyethyl (meth) acrylate is particularly preferable.

  When producing the laminated film of the present invention, a method of applying a resin composition containing an aqueous solvent to a polyester film before completion of crystal orientation, and completing crystal orientation by stretching and heat treatment is suitably used. . This is because heat treatment at a high temperature is possible, the adhesive force between the base material and the resin layer is improved, and a more uniform and thin resin layer can be provided. When the resin layer is formed by this method, the acrylic resin (c) is preferably an aqueous resin that can be dissolved, emulsified or suspended in an aqueous solvent from the viewpoint of environmental pollution and explosion resistance. Such acrylic resin that can be dissolved, emulsified or suspended in water is a copolymer or reactive emulsifier with a monomer having a hydrophilic group (acrylic acid, methacrylic acid, acrylamide, vinyl sulfonic acid and salts thereof, etc.). And emulsion polymerization using a surfactant, suspension polymerization, soap-free polymerization, and the like.

  The polymerization initiator is not particularly limited, but is a general radical polymerization initiator, for example, a water-soluble peroxide such as potassium persulfate, ammonium persulfate, hydrogen peroxide, or benzoyl peroxide or t-butyl hydroper Oil-soluble peroxides such as oxides or azo compounds such as azodiisobutyronitrile can be used.

  An acrylic resin having a monomer unit (c1) represented by formula (1), a monomer unit (c2) represented by formula (2), and a monomer unit (c3) represented by formula (3) In the composition, when the total solid weight of the metal oxide particles (b) and the polyester resin (a) having a fluorene structure is 100 parts by weight, it is preferably 1 part by mass or more and 10 parts by mass or less. More preferably, they are 2 mass parts or more and 9 mass parts or less, More preferably, they are 3 mass parts or more and 8 mass parts or less. By setting it as the above range, it becomes possible to further suppress the aggregation of the metal oxide particles (b). As a result, the refractive index and transparency of the resin layer are improved, and further, interference at the time of laminating the hard coat layer. Since it becomes possible to fully exhibit plaque suppression, it is preferable.

  In the resin layer (B layer) in the present invention, from the viewpoint of preventing aggregation between the metal oxide particles (b), the component (d1) derived from the oxazoline-based compound and / or the component (d2) derived from the melamine-based compound. It is preferable to contain.

The oxazoline-based compound (d ₁ ′) is not particularly limited as long as it has at least one oxazoline group or oxazine group per molecule, but the addition-polymerizable oxazoline group-containing monomer is polymerized alone, or other monomer The polymer type polymerized together is preferred.

  As addition-polymerizable oxazoline group-containing monomers, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline. These may be used alone or in a mixture of two or more. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition-polymerizable oxazoline group-containing monomer, such as alkyl acrylate, alkyl methacrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (Meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group), acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.), unsaturated nitriles such as acrylonitrile, methacrylonitrile; acrylamide, methacrylamide, N-alkylacrylamide N-alkyl methacrylamide N, N-dialkylacrylamide, N, N-dialkylmethacrylate (as alkyl groups, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group) , Cyclohexyl groups, etc.), vinyl esters such as vinyl acetate, vinyl propionate, acrylic acid, methacrylic acid with polyalkylene oxide added to the ester moiety, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, etc. , Α-olefins such as ethylene and propylene, halogen-containing α and β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride, α and β-unsaturated aromatics such as styrene and α-methylstyrene Group monomers and the like, one or more of these It may be used monomers.

The component (d2) derived from the melamine compound in the present invention is not limited to the melamine compound (d ₂ ′) described below, but the melamine compound (d ₂ ′) is an acrylic resin (c) or (c). In the case of forming a crosslinked structure with an acrylic resin other than the above or an oxazoline compound (d ₁ ′) or the like, a component (for example, a residue) derived from the melamine compound (d ₂ ′) is included.

Examples of the melamine compound (d ₂ ′) include melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, a compound partially or completely etherified by reacting a methylolated melamine with a lower alcohol, and These mixtures can be used. Specifically, a compound having a triazine and a methylol group is particularly preferable. Further, the melamine compound may be a monomer or a condensate composed of a dimer or higher polymer, or a mixture thereof. As the lower alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like can be used. The group has an imino group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group in one molecule, and an imino group type methylated melamine resin, a methylol group type melamine resin, or a methylol group type methyl group. Melamine resin, fully alkyl methylated melamine resin, and the like. Of these, methylolated melamine resins are most preferred. Further, an acidic catalyst such as p-toluenesulfonic acid may be used in order to accelerate the thermal curing of the melamine compound.

When such a melamine compound (d ₂ ′) is used, it is possible to suppress the aggregation of the metal oxide particles (b) in the process of drying the resin composition as described above, the transparency of the resin layer, The reflectance can be increased, and as a result, when a hard coat is laminated, a laminated film having excellent transparency, adhesiveness, and visibility can be obtained.

  In the present invention, the component (d1) derived from the oxazoline compound and / or the component (d2) derived from the melamine compound is optional as long as the effects of the metal oxide particles (b) and the acrylic resin (c) are not impaired. Can be used.

The amount of the oxazoline compound (d ₁ ′) which is a raw material of the component (d1) derived from the oxazoline compound and the melamine compound (d ₂ ′) which is a raw material of the component (d2) derived from the melamine compound is 10-50 mass parts are preferable with respect to a total of 100 mass parts of metal oxide particle (b) and acrylic resin (c), More preferably, it is 15-45 mass parts. By setting it as 10 mass parts or more, it becomes possible to express the effect of the component (C ₁ ) derived from the oxazoline-based compound and / or the component (C ₂ ) derived from the melamine-based compound in the resin layer.

In addition to the component (C ₁ ) derived from the oxazoline compound and / or the component (C ₂ ) derived from the melamine compound, other compounds such as carbodiimide compounds, epoxy compounds, aziridine compounds, amide epoxy compounds, titanium Titanate coupling agents such as chelates, methylolated or alkylolated urea compounds, acrylamide compounds, and the like can be optionally used.

  The coating method of the coating composition on the polyester film is preferably performed by an in-line coating method. The in-line coating method is a method of applying in the process of manufacturing a polyester film. Specifically, it refers to a method of coating at any stage from melt extrusion of a polyester resin to biaxial stretching followed by heat treatment and winding up, and is generally substantially non-obtainable after melt extrusion and rapid cooling. Crystalline unstretched (unoriented) polyester film (A film), then uniaxially stretched (uniaxially oriented) polyester film (B film) stretched in the longitudinal direction, or biaxially before heat treatment stretched further in the width direction It is applied to any one of stretched (biaxially oriented) polyester film (C film).

  In the present invention, the coating composition is applied to the polyester film of any one of the A film and B film before the crystal orientation is completed, and then the polyester film is stretched uniaxially or biaxially. It is preferable to employ a method in which a heat treatment (heat treatment) is performed at a temperature higher than the boiling point to complete the crystal orientation of the polyester film and a resin layer is provided. According to this method, since the polyester film can be formed and the coating composition can be applied and dried (that is, the resin layer is formed) at the same time, there is an advantage in manufacturing cost. Moreover, it is easy to make the thickness of the resin layer thinner in order to perform stretching after coating.

  Among them, a method of applying a coating composition to a film (B film) uniaxially stretched in the longitudinal direction or the width direction, and then stretching the film in the width direction or the longitudinal direction, followed by heat treatment is excellent. After applying to an unstretched film, the stretching process is less than once compared to the method of biaxial stretching, so it is difficult to cause defects or cracks in the composition layer due to stretching, and a composition layer excellent in transparency and smoothness This is because it can be formed.

  Here, as a method of applying the coating composition to the polyester film, a known coating method such as a bar coating method, a reverse coating method, a gravure coating method, a die coating method, a blade coating method, or the like can be used.

  Therefore, the best method for forming a resin layer in the present invention is to apply a coating composition using an aqueous solvent on a polyester film (base material layer (A layer)) using an in-line coating method, followed by drying, heat treatment ( It is a method of forming by heating. More preferably, the coating composition is in-line coated on the uniaxially stretched B film. In the method for producing a laminated film of the present invention, drying can be carried out in a temperature range of 80 to 130 ° C. in order to complete the removal of the solvent of the coating composition.

  Next, although the production method of the laminated film of the present invention will be described by taking as an example a case where a polyethylene terephthalate (hereinafter referred to as PET) film is used as the polyester film, it is not limited thereto. First, PET pellets are sufficiently vacuum-dried, then supplied to an extruder, melt extruded into a sheet at about 280 ° C., and cooled and solidified to produce an unstretched (unoriented) PET film (A film). This film is stretched 2.5 to 5.0 times in the longitudinal direction with a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented PET film (B film). The coating composition of the present invention prepared at a predetermined concentration is applied to one side of the B film.

  At this time, surface treatment such as corona discharge treatment may be performed on the coated surface of the PET film before coating. By performing surface treatment such as corona discharge treatment, the wettability of the coating composition to the PET film is improved, the coating composition is prevented from being repelled, and a resin layer having a uniform coating thickness can be formed. After coating, the edge of the PET film is held with a clip and guided to a heat treatment zone (preheating zone) of 80 to 130 ° C., and the solvent of the coating composition is dried. After drying, the film is stretched 1.1 to 5.0 times in the width direction. Subsequently, it is guided to a heat treatment zone (heat setting zone) at 200 ° C. to 250 ° C., and heat treatment is performed for 1 to 30 seconds to complete crystal orientation.

  In this heat treatment step (heat setting step), a relaxation treatment of 3 to 15 may be performed in the width direction or the longitudinal direction as necessary. Since the laminated film thus obtained becomes a laminated film excellent in adhesion to the hard coat layer and adhesiveness under high temperature and high humidity, it can be suitably used for display applications.

[Characteristic measurement method and effect evaluation method]
The characteristic measurement method and effect evaluation method in the present invention are as follows.

(1) Base material thickness (T)
Based on JIS-C2151, the substrate thickness of 15 points was measured at random from the laminated film with a micrometer (Mitutoyo Thickness Gauge TNKK547-401), and the average value was defined as the substrate thickness (T).
(2) Thickness of resin layer (B layer) The thickness of the resin layer (B layer) on the polyester film was measured by observing a cross section using a transmission electron microscope (TEM). As for the thickness of the resin layer (B layer), the thickness of the resin layer (B layer) was read from an image taken with a TEM at a magnification of 200,000 times. A total of 20 resin layer (B layer) thicknesses were measured and averaged.

(3) Amount of carboxyl end groups
It was measured by the following method according to the method of Malice (references MJ Malice, F. Huizinga. Anal. Chim. Acta, 22 363 (1960)).
2 g of polyester resin or polyester film was dissolved in 50 mL of o-cresol / chloroform (weight ratio 7/3) at a temperature of 80 ° C., titrated with a 0.05 N KOH / methanol solution, the terminal carboxyl group concentration was measured, / Indicated by the value of polyester 1t. In addition, the indicator at the time of titration used phenol red, and the place where it changed from yellowish green to light red was set as the end point of titration.

(4) Minute endothermic peak (Tmeta)
The film was measured with a differential scanning calorimeter (DSC Q100 manufactured by TA Instruments) at a temperature rising rate of 20 ° C./min in the range of 30 ° C. to 280 ° C. The minute endothermic peak temperature before the polyester crystal melting peak in the differential scanning calorimetry chart obtained by this measurement was defined as Tmeta (° C.).

(5) Adhesiveness with the laminate The UV curable resin mixed in the following ratio on the resin layer (B layer) side of the laminate film is uniform so that the thickness after curing using a bar coater is 2 μm. It was applied to.
-Adjustment of hard coating agent-Titanium dioxide fine particles (Ishihara Sangyo Co., Ltd., TTO-55B): 30 parts by mass-Carboxylic acid group-containing monomer (Toa Gosei Co., Ltd., Aronix M-5300): 4.5 masses Part / Cyclohexanone: 65.5 parts by mass The above mixture was dispersed by a sand grinder mill to prepare a dispersion of titanium dioxide fine particles having an average particle diameter of 55 nm.
To the above dispersion of titanium dioxide fine particles, dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd., DPHA) and photoinitiator (manufactured by Ciba Geigy, Irgacure 184) are added in a total amount of monomers (dipentaerythritol 5% by mass with respect to the total amount of the hexahexaacrylate and the anionic monomer) and mixed to adjust the refractive index of the hard coat layer to 1.65.

Next, the integrated irradiation intensity was set with a condensing type high-pressure mercury lamp (H03-L31, manufactured by Eye Graphics Co., Ltd.) having an irradiation intensity of 120 W / cm set at a height of 9 cm from the surface on which the UV curable resin layer was laminated. Ultraviolet rays were irradiated so as to be 300 mJ / cm 2 and cured to obtain a hard coat laminated film in which a hard coat layer was laminated on the laminated film. In addition, an industrial UV checker (manufactured by Nippon Batteries Co., Ltd., UVR-N1) was used for measuring the cumulative irradiation intensity of ultraviolet rays. About the obtained hard coat laminated film, 100 crosscuts of 1 mm 2 are put on the hard coat laminated surface of the obtained hard coat laminated film, and “Cello Tape” (registered trademark) (made by Nichiban Co., Ltd., CT405AP) is pasted. After pressing with a hand roller at a load of 1.5 kg / cm 2, it was peeled rapidly in the direction of 90 degrees with respect to the hard coat laminated film. Adhesiveness was evaluated in four stages according to the number of remaining lattices. The measurement was carried out 10 times, and the average value was used for evaluation. C is a practically problematic level, B is a practical level, and A and S are good. Further, when the number of remaining lattices was less than 80, the surface of the separated lattice portion was observed by SEM, and the separation interface (where the separation occurred) was identified. In addition, in the column of the peeling interface in the table, among the lattices where peeling occurred, the place where peeling occurred most frequently was shown. Moreover, when surface observation was not implemented, "-" was shown in the column of the peeling interface in a table | surface.
S: 90 to 100 remaining A: 80 to less than 90 remaining B: 50 to less than 80 remaining C: 0 to less than 50 remaining.

(6) Moist heat adhesion The hard coat layer was laminated on the resin layer side of the laminate film by the same method as in (5) to obtain a hard coat laminate film. Further, the obtained hard coat laminated film was left in a constant temperature and humidity chamber having a temperature of 75 ° C. and a relative humidity of 90% for 240 hours to obtain a sample for wet heat adhesion test. The obtained wet heat adhesion test sample was subjected to an adhesion test in the same manner as in (5), and was evaluated in four stages according to the number of remaining lattices. The measurement was carried out 10 times, and the average value was used for evaluation. C is a practically problematic level, B is a practical level, and A and S are good. Moreover, the peeling interface was identified by the same method as (5).
S: 90 to 100 remaining A: 80 to less than 90 remaining B: 50 to less than 80 remaining C: 0 to less than 50 remaining.

(7) Interference spot visibility By the method similar to (5), a hard coat laminated film in which a hard coat layer (refractive index of 1.65) having a thickness of 2 μm was laminated on the laminated film was obtained. Next, a sample having a size of 8 cm (laminated film width direction) × 10 cm (laminated film longitudinal direction) was cut out from the obtained optical laminated film, and a black glossy tape (manufactured by Yamato Co., Ltd.) was formed on the opposite surface of the hard coat layer. , Vinyl tape No. 200-50-21: black) was bonded so as not to bite the bubbles.

Place this sample in a dark room 30 cm directly under a 3-wavelength fluorescent lamp (manufactured by Panasonic Corporation, 3-wavelength daylight white (F · L 15EX-N 15W)), and visually observe the degree of interference spots while changing the viewing angle. The following evaluation was performed. A or higher was considered good.
S: Interference spots are almost invisible A: Interference spots are slightly visible B: Weak interference spots are visible
C: Interference spots are strong.

(8) Evaluation of flatness 1 m in the longitudinal direction of the film and 1 m in the width direction are cut out and placed on the flat table, and the flat table is used by using a jig in which a cloth is wound around the rod from the film end to the opposite end. Remove the air between the film and the film. After leveling for 30 seconds in that state, the number of lifts at the end is measured. The number of lifts of the film having a length in the longitudinal direction of 15 mm or more, a length in the width direction of 40 mm or more, and a height of 1.0 mm or more was counted. The evaluation was performed three times, and the average value was evaluated as follows. A and S were accepted.
S: Less than 1 place A: 1 place or more and less than 5 places B: 5 places or more.

  A more specific description will be given based on examples of the present invention. However, the present invention is not limited to the following examples.

First, the polyester resin (a), metal oxide particles (b), acrylic resin (c), oxazoline compound (d1), melamine compound (d2), and method for adjusting the coating composition used in this example are described below.
・ Polyester resin (a)
A polyester resin having the following copolymer composition was used as the polyester resin (a). The composition ratios of the following dicarboxylic acid component and diol component indicate values when the total dicarboxylic acid component and the total diol component are each 100 mol%. The molar ratio of all dicarboxylic acid components to all diol components is 1: 1.
(Dicarboxylic acid component)
Succinic acid: 100 mol%
(Diol component)
9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene: 90 mol%
Ethylene glycol: 10 mol%
・ Metal oxide particles (b)
Zirconium oxide dispersion SZR-CW (manufactured by Sakai Chemical Industry Co., Ltd., zirconium oxide particles: number average particle diameter 20 nm), which is metal oxide particles, was used.

・ Acrylic resin (c)
“Sannaron” (registered trademark) WG-658 (solid content concentration 30% by weight) manufactured by Shannan Synthetic Chemical Co., Ltd. was used.

Oxazoline compound “Epocross” (registered trademark) WS-500 (solid content concentration: 40% by weight) manufactured by Nippon Shokubai Co., Ltd. was used.

Melamine compound “Nikarak” (registered trademark) MW12LF manufactured by Sanwa Chemical Co., Ltd. was used.

-Paint composition 50 parts by mass of metal oxide particles (b), 5 parts by mass of acrylic resin (c) as a solid content, and a pH adjuster (sodium carbonate) are added to pure, and a homomixer is used. And a metal oxide (b) dispersion having a pH of 10.0 was obtained.

  To this metal oxide (b) dispersion, 50 parts by mass of the polyester resin (a) as a solid mass, 20 parts by mass of the oxazoline-based compound (d1) as a solid mass, and the melamine compound (e1) as a solid mass are added. After adding 40 parts by mass, the mixture was mixed to obtain a coating composition 1 having a pH of 10.0.

Example 1
PET pellets (intrinsic viscosity 0.63 dl / g) substantially free of particles are vacuum dried at a temperature of 160 ° C. for 4 hours under a reduced pressure of 1 kPa, then supplied to an extruder and melted at 285 ° C. The sheet was extruded from the die into a sheet shape, wound around a mirror casting drum having a surface temperature of 25 ° C. using an electrostatic application casting method, and cooled and solidified. This unstretched film was heated to 90 ° C. and stretched 3.4 times in the longitudinal direction to obtain a uniaxially stretched film (B film).

  Next, the coating composition 1 was applied to the corona discharge treated surface of the uniaxially stretched film using a bar coat. The both ends in the width direction of the uniaxially stretched film coated with the coating composition are held by clips and guided to a preheating zone, and the ambient temperature is set to 75 ° C. Subsequently, the ambient temperature is set to 110 ° C using a radiation heater, and then the ambient temperature. The coating composition was dried at 90 ° C. to form a resin layer (B layer). Continuously stretched 3.5 times in the width direction in a 120 ° C heating zone (stretching zone), and then heat treated for 19 seconds in a 235 ° C heat treatment zone (heat setting zone) to complete the crystal orientation. Got. In the obtained laminated film, the thickness of the PET film was 125 μm, and the thickness of the resin layer was 40 nm.

  The characteristics of the obtained laminated film are shown in the table. The results were excellent in initial adhesion with the hard coat layer and in wet heat resistance.

(Examples 2, 3, and 4, Comparative Examples 1 and 2)
A laminated film was obtained in the same manner as in Example 1 except that the amount of the carboxyl group terminal of the laminated film was as shown in the table.

(Examples 5, 6, and 7, Comparative Examples 3 and 4)
A laminated film was obtained in the same manner as in Example 1 except that the heat treatment temperature in the heat setting zone was changed to the temperature described in the table.

(Examples 8, 9, and 10)
A laminated film was obtained in the same manner as in Example 1 except that the film thickness of the resin layer (B layer) was changed as described in the table.

(Example 11, Comparative Examples 5 and 6)
A laminated film having a substrate thickness of 50 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature and time in the heat setting zone were changed to the temperatures described in the table.

(Examples 12 and 13, Comparative Example 7)
A laminated film having a substrate thickness of 188 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature and time in the heat setting zone were changed to the temperatures described in the table.

(Examples 14 to 18)
A laminated film was obtained in the same manner as in Example 1 except that the coating composition in which the solid content weight ratio in the coating liquid composition part was changed as described in the table was used.

Claims (7)

A laminated film having a base material layer (A layer) containing a polyester resin as a main component and a resin layer (B layer) adjacent to at least one surface of the A layer, the carboxyl terminal of the polyester resin of the A layer A laminated film having a base amount of 20 eq / ton or more and 60 eq / ton or less and satisfying the following formula 1.
230 ≦ Tmeta + 0.05T (Formula 1)
(However, Tmeta is a minute endothermic peak temperature (° C.) obtained by differential scanning calorimetry (DSC) of the laminated film, and T is the thickness (μm) of the laminated film.) The laminated film according to claim 1, wherein the laminated film satisfies the following formula 2.
Tmeta + 0.05T ≦ 245 (Formula 2) The laminated film according to claim 1 or 2, wherein the resin layer (B layer) has a thickness Tb of 5 to 120 nm.   The laminated film according to claim 1, wherein the resin layer (B layer) is a layer mainly composed of a polyester resin. The resin layer (B layer) is derived from the polyester resin (a), the metal oxide particles (b), the acrylic resin (c), the component (d1) derived from the oxazoline compound and / or the melamine compound. The laminated | multilayer film in any one of Claims 1-4 containing the component (d2) to do. The resin layer (B layer) heats a coating composition containing a polyester resin (a), metal oxide particles (b), an acrylic resin (c), an oxazoline compound and / or a melamine compound. The laminated film according to any one of claims 1 to 5. The laminated film according to any one of claims 1 to 6, which is used for display applications.